Big latency on CISCO 7200 ATM circuit

Discussion in 'Cisco' started by Raymond Jimenez, Dec 15, 2003.

  1. I've got a CISCO 7200 with ATM 4MB. I've started noting that when the
    circuit gets to 3.2Mb, the delays start to be high (200ms), and when
    the circuit tops at 3.6Mb, the delay can be one second or above. I can
    understand the delay when it tops due to queueing, but not when it is
    below the maximum usage. Haven't seen great drops nor retransmisions.
    Have gone through the conf, but nothing suspicious. Any ideas?
    rj
     
    Raymond Jimenez, Dec 15, 2003
    #1
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  2. Hello, Raymond!
    You wrote on 15 Dec 2003 15:51:04 -0800:

    RJ> I've got a CISCO 7200 with ATM 4MB. I've started noting that
    RJ> when the circuit gets to 3.2Mb, the delays start to be high
    RJ> (200ms), and when the circuit tops at 3.6Mb, the delay can be
    RJ> one second or above. I can understand the delay when it tops
    RJ> due to queueing, but not when it is below the maximum usage.
    RJ> Haven't seen great drops nor retransmisions.
    RJ> Have gone through the conf, but nothing suspicious. Any ideas?
    RJ> rj

    Did you check with the carrier PCR, SCR and MBS settings? We had precisely the
    same problem - RTT around 1s - when carrier had VBR-nrt class of service
    configured on their switches with 3Mbps PCR and 1.5Mbps SCR, and another group
    of the same company configured UBR with 3Mbps PCR on our routers.

    "show atm pvc" would be helpful.

    With best regards,
    Andrey.
     
    Andrey Tarasov, Dec 16, 2003
    #2
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  3. Raymond Jimenez

    CBarnes205 Guest

    What type of ATM module is installed? Have you looked at the memory?
    Look for buffer overruns. You mentioned queueing. Are you running
    any sort of QOS on the circuit? How is the PVC configured; VBR-RT,
    VBR-NRT, ABR. Make sure you and the provider have the same settings
    on the PVC; PCR, SCR, MBR.
    A misconfiguration on you PVC in the cloud my be the cause of your
    issue.

    (Raymond Jimenez) wrote in message news:<>...
    > I've got a CISCO 7200 with ATM 4MB. I've started noting that when the
    > circuit gets to 3.2Mb, the delays start to be high (200ms), and when
    > the circuit tops at 3.6Mb, the delay can be one second or above. I can
    > understand the delay when it tops due to queueing, but not when it is
    > below the maximum usage. Haven't seen great drops nor retransmisions.
    > Have gone through the conf, but nothing suspicious. Any ideas?
    > rj
     
    CBarnes205, Dec 16, 2003
    #3
  4. Yes, I've seen the same thing Andrey! Raymond, your carrier most likely
    misconfigured the PVC.

    Mike

    "Andrey Tarasov" <> wrote in message
    news:brlqkd$1gni$...
    > Hello, Raymond!
    > You wrote on 15 Dec 2003 15:51:04 -0800:
    >
    > RJ> I've got a CISCO 7200 with ATM 4MB. I've started noting that
    > RJ> when the circuit gets to 3.2Mb, the delays start to be high
    > RJ> (200ms), and when the circuit tops at 3.6Mb, the delay can be
    > RJ> one second or above. I can understand the delay when it tops
    > RJ> due to queueing, but not when it is below the maximum usage.
    > RJ> Haven't seen great drops nor retransmisions.
    > RJ> Have gone through the conf, but nothing suspicious. Any ideas?
    > RJ> rj
    >
    > Did you check with the carrier PCR, SCR and MBS settings? We had precisely

    the
    > same problem - RTT around 1s - when carrier had VBR-nrt class of service
    > configured on their switches with 3Mbps PCR and 1.5Mbps SCR, and another

    group
    > of the same company configured UBR with 3Mbps PCR on our routers.
    >
    > "show atm pvc" would be helpful.
    >
    > With best regards,
    > Andrey.
    >
     
    Mike Gallagher, Dec 16, 2003
    #4
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